Fossil bones from the largest dinosaurs ever known to walk Australia were on Thursday unveiled in a find, which scientists said, shed new light on the country's prehistoric past.
The remains of two Titanosaurs, nicknamed Cooper and George, were uncovered by farmers near the outback town of Eromanga in south-west Queensland state in 2005 and 2006, but were kept secret to allow investigation by dinosaur-hunting scientists.
"We were mustering cattle on motorbikes when we found fragments of the big one, Cooper. My 14-year-old son found the other one," farmer Stuart MacKenzie said.
Fossilised leg bones showed the pair were 6-7 metres longer than the biggest sauropod dinosaur previously found in Australia, Queensland Museum Curator Scott Hocknull said.
The finding is likely to change understanding of how big dinosaurs grew in Australia, and their range across the country, with the latest discovery being further south than previous discoveries.
"The great thing about Australia is that there are always new things being found and it's all new to science. It's the tip of the iceberg," Hocknull said.
Titanosaurs, with their long necks and tails, were among the heaviest creatures to walk the earth, weighing up to 100 tonnes, and were one of the last sauropods of the Cretaceous Period.
They roamed Australia 98 million years ago, when the continent was greener and wetter, living on plants until prehistoric climate change saw their extinction.
They were named after the Titans of Greek myth and lived in mainly southern parts of the ancient supercontinent Gondwana.
Hocknull said Cooper's right humerus weighed 100 kilograms (220 pounds) and was a rare complete bone measuring 1.5 metres (5 feet) in length. The two dinosaurs would have been at least 26 metres long, but may even have rivalled the largest dinosaur ever found, the 35-metre Argentinosaurus, he said.
Fossil records in Australia are relatively rare because of the country's vast size and low population, which has hampered proper exploration by scientists.
"The fact is it is just not populated enough for people to find things. Almost all of the dinosaur discoveries are made by landowners, and the percentage that recognise they have found something different is pretty small," Hocknull said.
The latest findings could help scientists learn lessons about climate change and a generational drought currently being felt by Australians and blamed on global warming.
"If we don't know what happened to our animals and plants in the past, we cannot tell what happens in the future," he said.